Nutritional compositions for infants generally seek to mimic the composition and function of human breast milk. Lactoferrin is an 80-kDa member of the transferrin family of iron-binding glycoproteins, and is one of the primary proteins in human milk. Lactoferrin has the capacity to reversibly bind two iron cations, even at low pH, and can facilitate iron uptake in the human intestine. Functionally, lactoferrin regulates iron absorption and can bind iron based free radicals as well as donate iron for an immunological response. Additionally, lactoferrin exhibits antibacterial activity. Thus, it would useful to include lactoferrin in commercial infant formulas.
However, the use of lactoferrin in infant formulas has been limited by the lack of large-scale, commercially useful sources. Bovine lactoferrin, which has about 69% sequence homology to human lactoferrin, can be obtained from cow's milk by a variety of purification methods, but such processes are inefficient for widespread commercial use. Other non-human lactoferrins include porcine lactoferrin, equine lactoferrin, buffalo lactoferrin, goat lactoferrin, murine lactoferrin, and camel lactoferrin, but similar production inefficiencies exist.
The concentration of lactoferrin in bovine whey, for example, is generally only about 10 to 100 mg/liter. Stabilized fluid bed adsorption, also called Expanded Bed Adsorption (EBA) is one process for obtaining proteins from a raw material, such as bovine lactoferrin from cow's milk sources. EBA enables the isolation of biomolecules, such as proteins and plasmids, directly from a crude feed stock using a particulate chromatographic matrix, in which the matrix remains fluidized during loading of the feed stock and optionally during elution. Because the matrix is fluidized during loading, solids and undesired materials pass through the matrix, which avoids fouling of the chromatographic material. Thus, EBA can, in certain circumstances, combine the effects of centrifugation, filtration, concentration and purification into a single process, thereby saving time and minimizing pre-processing purifying steps. However, current EBA technology has several disadvantages in isolating lactoferrin from milk sources. In particular, current EBA technology still uses a relatively large volume of liquid and also uses a high concentration of sodium hydroxide (e.g. 200 mM) during elution of the lactoferrin, which may cause irreversible structural changes due to denaturing of the protein.
Additionally, non-human mammalian milk sources contain other useful proteins, including lactoperoxidase, α-lactalbumin, β-lactoglobulin, immunoglobulins, glycopeptides, glycomacropeptide, whey protein isolates, and lysozyme. These proteins and mixtures also may useful as food ingredients or nutritional supplements. Thus, there is a need for improved processes for isolating and purifying lactoferrin and other proteins from milk sources on a commercial scale for use in nutritional products, such as infant formulas.